Gas lift is a form of artificial lift for liquid hydrocarbon wells. Gas bubbles are introduced into the vertical production tube that outlets the hydrocarbon resource from the well. The rising bubbles of injected gas reduce the hydrostatic pressure of the fluid column in the production tube as compared with the reservoir below and aerate the fluid to reduce its density. The inherent reservoir pressure below is then able to lift the hydrocarbon fluid out of the wellbore via the production tube.
A gas lift mandrel is a device installed in or on the tubing string of a gas lift well. Each gas lift mandrel is fitted with one or more gas lift valves. In a side-pocket type of gas lift mandrel, the gas lift valve can be installed and removed by wireline while the mandrel is still in the well, eliminating the need to pull the production tubing to repair or replace the gas lift valve.
One or more gas lift valves may reside in each gas lift mandrel to inject pressurized gas from the well casing annulus into the production tubing. Pressures in the production tubing and in the casing annulus cause the gas lift valves to open and close, thus allowing gas to be injected into the fluid in the tubing to cause the fluid to rise to the surface.
A barrier-type mandrel and associated gas lift barrier valves prevent well fluid from flowing backwards from the production tubing into the well casing space when pressurized gas is not being injected, and maintain a barrier during valve replacement operations when one of the gas lift barrier valves is being removed for replacement or repair.